In the recovery of metals, problems occur when one or more halides are present in the feed material. For example, a zinc sulphate solution with 200 mg/L each of fluoride and chloride can result from the leaching of a zinc oxide fume from a lead smelter slag fuming operation. The dissolved halides increase aluminum corrosion rates in electrowinning and can result in hygiene problems, particularly from emissions during electrowinning.
Apart from halide removal, it may be desirable to extract sulphate from metal sulphate solutions. While high extraction efficiencies of halides would generally be desirable, sulphate extraction requirements would be variable depending on plant sulphate bleed requirements and other factors.
It, accordingly, is an object of the present invention to provide a method for removal of halides from hydrometallurgical or other industrial aqueous solutions with the flexibility to vary the amount of sulphate or acid being co-extracted with the halide. The invention is the basis of the Teck Cominco Halogon™ process.